Study on the relationship between isolation of mycobacteria and classical microbiological and chemical indicators of water quality in swimming pools.

Observation of skin lesions in patients who frequent swimming pools in the dermatology section of the Nancy Hospital, coupled with isolation of Mycobacteria marinum led to a preliminary survey of 20 swimming pools in the Lorraine region for Mycobacteria. Six representative pools were then chosen for more in-depth research during 1977 and 1978: 3 chlorinated, 2 brominated and 1 ozonated pool. The following parameters were analyzed: chemical (pH, conductivity, residual disinfectant, and oxidizable matter by potassium permanganate); microbiological (standard plate counts, total and faecal coliforms, Streptococci, Clostridia, Mycobacteria, and pathogenic Staphylococci). During the survey, different species were isolated: saprophytic Mycobacteria such as M. gordonae, M. flavescens, M. terrae, M. aurum and M. parafortuitum; and opportunistic pathogens such as M. marinum, M. kansasii, and M. fortuitum. There was no correlation between the presence of Mycobacteria and classical microbiological indicators. In one pool, M. marinum was repeatedly isolated, this same pool supplied by thermal water was being used by some patients with skin granuloma. Increased chlorination eliminated this pathogenic species. The level of saprophytic Mycobacteria was very low while opportunistic Mycobacteria were absent in pools with a residual chlorine concentration of only 0.5--0.6 mg/l. The same results were found for brominated pools with a residual of 2 mg/l, and for the ozonated pool without a residual. The Mycobacteria contamination was due partly to the water which replaced eliminated water and partly to swimmers and pool surfaces (walls, floor).